DESCRIPTION (From the Applicant's Abstract): Presenilin-1 (Psi) protein is involved in a variety of critical physiological processes including embryogenesis, CNS development, cell death, and pathogenesis of Alzheimer's disease (AD). Psi influences mammalian development and neuronal apoptosis by controlling the proteolytic cleavage of Notch 1 receptor, and PS1 also causes pathogenesis of early-onset AD (FAD) by altering the processing of b-amyloid precursor protein (APP). Thus, PS1 gene regulation plays a crucial role to control these events. However, we do not yet understand the precise regulatory mechanisms controlling the transcription of the PS1 gene, and in the absence of that information it has been difficult to target the PS1 gene locus in designing therapies to control mammalian development and AD. The experiments proposed in this application will elucidate the regulatory mechanisms of PS1 gene transcription. A secondary aim of this proposal tests the hypothesis that inhibition of PS1 gene expression is mediated by p53-activation. This experiment is important because PS1 expression is linked to (i) Notch 1 mediated cell fate decision during development, (ii) neuronal apoptosis during aging, and (iii) pathogenesis of FAD. The proposed specific aims are to: (1) Identify and characterize trans-acting factors interacting with the human PS1 gene fragment (-118 to +178); (2) Clone novel trans-acting factors binding to elements (-22 to -6), (+75 to +102), (+130 to +143), and identify partner proteins interacting with Ets factors; and (3) Elucidate the mechanism of Psi gene regulation by Ets and p53 proteins. Roles of Ets, p53, and other trans-acting factors in PS1 transcription will be established by antibody supershift, Dnase I foot printing, and in vivo expression of genes encoding these factors. Novel trans-acting factors and Ets partners will be cloned by yeast one-hybrid and two-hybrid systems respectively. Interaction of p53 and Ets transcription factors will be determined by pull down assay. These experiments will provide detailed analysis of trans-acting factors that are likely to be involved in mammalian development and also in the pathogenesis of both early-onset and late-onset Alzheimer's disease.